Bast ribbon processing apparatus and method of decortication

ABSTRACT

A method and apparatus for decortication of fibrous plant stalks, involving first flattening the plant stalk, splitting the two substantially planar stalk sides one from the other; then bending each planar stalk such that the flat stalk piece with the hurd is on the outside of the bend and fibrous bast on the inside of the bend; separating the segments such that the bast begins to pull away from the hurd that spans the gap between the bent segments; peeling the bast from the broken hurd. The resultant bast fiber ribbon is valuable to textile and composite manufacturing industries while the leftover hurd is suitable for a wide range of uses.

FIELD OF THE INVENTION

The present invention relates to the field of ribbon decortication of fibrous plant stalks, in particular hemp.

BACKGROUND OF THE INVENTION

Decortication of fibrous plant stalks provides three distinct carbon absorbing commodities from a single crop. The first and most valuable is bast ribbon, used for composites, textiles and rope. The second is hurd core, used for hempcrete (non-structural concrete), absorbents, bioplastics and paper to name but a few. The third commodity obtained is highly nutritious hemp seed that is used for human consumption (when dehulled), animal feed, biodiesel and oil-based paints. Depending on their species, textile producing plants are classified into seed fibers (cotton, kapok) or bast fibers (kenaf, flax, hemp, jute, and ramie).

Bast fiber is plant fiber collected from the phloem (the “outer bark”, sometimes called “skin”) or bast surrounding the stem of certain plants. It supports the conductive cells of the phloem and provides strength to the stem. The stalk of a hemp plant is generally of substantially circular cross-section, having a fibrous outer layer ‘bast’ and an inner woody core ‘hurd’.

Hemp stalks are comprised of (beginning from the outside of the plant) an epidermis, cortex, phloem, cambium, xylem & pith. The cortex contains the highest tensile strength and is referred to as primary fibers. Prized by textile and composite manufacturing, it must first shed its epidermis by mechanical, chemical or microbial processes. Mechanical degumming scrubs the rough epidermis off the plant without damaging the cortex and is widely used in spinning mills. Retting or dew-retting involves leaving cut stalks in the field then turning after a period of time to promote microbial degradation. This method, although also widely used, introduces inconsistency due to unpredictable weather. Chemical or water-retting are typically utilized in locations where environmental controls are non-existent. The inner phloem, cambium, xylem and pith (hurd) is composed of 44% alpha-cellulose, 25% hemicellulose, and 23% lignin. Hurd accounts for approximately 75% of the dry weight of the plant stalk.

Owing to their different physical properties and chemical composition, bast and hurd are suitable for a wide range of industrial applications including bio-composites, construction materials, textiles, insulation, bedding, absorbents, paper production, bioplastics, ropes and twines among others. For millennia, hemp was grown for its bast fiber, primarily for textile applications (clothing, sails, ropes), while hurd was used to build hempcrete homes (by combining with water and lime), produce paper and provide animal bedding. Revival of hemp production during the last few decades in Canada was primarily for seeds for human consumption only. In the USA growth has been in CBD production, grown for its natural anti-inflammatory and non-psychoactive healing properties. Only recently, the potential uses of the bast and hurd and their carbon-absorbing attributes are being rediscovered to the mainstream and driving innovation into separating the bast from the hurd with zero cross-contamination. A 0.3% THC dual-purpose variety of preferably monoecious hemp is sown into well-drained and fertile soil when the average ground temperature reaches a minimum 8° C. Watering is provided for two weeks, in rows preferably spaced 20 cms apart and 2 cms deep. The crop is harvested early, when the seeds have set and the male plants are still viable. There is a 2-3 week window to cut the tops off into the field at 1 to 2 meters off the ground. The remaining 1 to 2 meters of remaining plant stalk is recovered as feedstock for the disclosed invention. The cut tops are collected using a combine harvester within a week of being laid in the field for seed (based on moisture level) while the leftover chaff can be collected as grazing feed, low-grade CBD production or left in the field to enhance the soil. In addition, fiber-only varieties of hemp sown in a similar manner produce the same result if the bushy tops are cut off prior to harvesting and stalks are then cut in half using a parallel swath cutter by ValtechTM group.

Decortication is a general term for the removal of the bark, husk, or outer layer of fibrous plant crops. In hemp fiber production, decortication is used to refer to the separation of the bast and hurd. There is currently no mechanical method to commercially peel the bast from the hurd, herein referred to as ribbon decortication. Hand-peeling the stalk is the only way to obtain commercially produced ribbon bast fiber in China, which has continued since they began using it to produce fine clothing.

A number of proposals have been suggested for separating the bast from the hurd. The principal category of decortication is mechanical separation. Traditionally scutching has been the most widely used. Scutching involves manually beating the hemp stalk until the hurd is dislodged from the fiber. The beating loosens the bonds between the bast and the hurd. Current large-scale operations require multiple passes to obtain textile-quality fiber. Other known decortication methods include the use of ultrasonic sound waves to generate vibrations to break the bonds between fiber and hurd without cross-contamination, along with chemical baths that produce environmental consequences.

SUMMARY OF THE INVENTION

In one aspect, there is provided a method for decorticating a length of a plant stalk, the method comprising: a) passing the length of plant stalk between opposed rollers to flatten the plant stalk into two substantially planar stalk sides with adjoining edges; b) interposing and passing a splitter between the two stalk sides so as to sever the adjoined edges, creating two stalk pieces, each comprising a bast layer and hurd; c) supporting fore and aft sections of each stalk piece in fore and aft chutes; d) rotating the fore and aft chutes with respect to each other to bend each stalk piece, with the hurd on an outer radius and bast on an inner radius until the hurd is broken, without severing the bast layer; e) peeling the bast layer from the hurd by acting on a section of the bast layer connecting the broken hurd pieces and moving that section of the bast layer away from the broken, supported stalk pieces; and f) ejecting the bast layer and hurd to collection locations.

The peeled bast may form an acute angle with the unpeeled bast at a point of peeling off the hurd.

Peeling may occur at substantially rounded edges of the fore and aft chutes.

Peeling may be provided by a peeling plate abutting an inner surface of the bast.

The method may comprise wiping the bast from the peeling plate.

The method may, during peeling, move the broken stalk pieces in a direction generally opposite the movement of the section of bast connecting said broken stalk pieces.

The method may further comprise gripping the stalk pieces in the chutes during bending.

During bending, the fore and aft chutes may contain substantially equal portions of the stalk pieces and the chutes rotate relative to each other to break the hurd at substantially mid-length.

The fore and aft chutes may rotate relative to each other, from an aligned orientation to substantially parallel orientation.

The method may urge the peeled bast into contact with the peeling plate during peeling, preferably using a passive roller.

The method may move the fore chute away from the aft chute, after breaking the hurd that continues to be driven through the splitter and rollers.

According to a second aspect there is provided apparatus for decorticating a length of a plant stalk comprising: opposed rollers for receiving and flattening the plant stalk into two substantially planar stalk sides with adjoining edges; a splitter positioned downstream of the rollers, so as to sever the adjoined edges, creating two stalk pieces, each comprising a bast layer and hurd; fore and aft chutes for receiving and supporting the stalk pieces; an actuator for rotating the fore and aft chutes relative to each other to bend and break the stalk pieces, without severing the bast layer; a peeling plate moveable between fore and aft chutes for peeling the bast layer from the hurd; and ejection chutes for ejecting the bast layer and hurd to collection locations;

The fore and aft chutes may comprise rounded edges.

The apparatus may comprise a wiper engaging a leading edge of the peeling plate.

The apparatus may comprise clamps in the fore chutes for holding stalk pieces during bending.

The apparatus may comprise a roller biased against the peeling plate during peeling.

BRIEF DESCRIPTION OF THE DRAWINGS

Various objects, features and advantages of the invention will be apparent from the following description of embodiments of the invention, as illustrated in the accompanying drawings. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of various embodiments of the invention.

FIG. 1 is a side view of a decorticating machine.

FIG. 2 is an isometric view of a decorticating machine.

FIG. 3 is a top view of a decorticating machine.

FIG. 4 is an end view of a decorticating machine.

FIG. 5 is a cross-sectional detailed view of the embodiment shown in FIGS. 1-4 showing the infeed and splitter assembly with passage of a hemp stalk just prior to being split in half.

FIG. 6 is a cross-sectional view showing the split stalk entering a bending chute prior to bending.

FIG. 7 is a cross-sectional view showing the operation during clamping and bending.

FIG. 8 is a cross-sectional view as the bending chute completes the bend and moves away from the stationary chute.

FIG. 9 is a cross-sectional view showing the hurd separating from the bast.

FIG. 10 is a cross-sectional view showing a peeling plate making initial contact with the exposed bast fiber.

FIG. 11 is a cross-sectional view of the embodiment, showing downward passage of the peeling plate and interaction of the tensioning rolls with the in-feed roller assembly.

FIG. 12 is a side view of the machine with the bast extraction conveyor assembly interacting with each peeling plate leading edge.

DETAILED DESCRIPTION OF PREFFERED EMBODIMENTS

As shown in the drawings, embodiments of the present invention include a bast decorticating device having a frame 13, an infeed assembly, a splitter assembly 2, a bending and bast preparation assembly, a peeling plate assembly 11, a bast wiper assembly; and hurd discharge chutes 10. The machine operates continuously on lengths of stalks 8, which are infed one at a time. The stalks are flattened between opposing rollers 1, split apart, bent and separated into bast and hurd.

The machine can process thick stalks located adjacent to narrow stalks, laid out in a row while providing an allowance for stalks that are not exactly the same length (+/- 15 cms). The infeed is built to accept the top stem of pre-harvested hemp. Plants may be cross-cut in the field, with the lower stalks cut every 22 cms and loaded onto an elevator, each stalk length being added timed to each cycle of the peeling plates.

The decortication processes may be operated at a stand-alone stationary machine or combined with a harvesting implement in the field. It is understood a stationary processing method would follow flax harvesting and processing best practices to provide a means for a row of stalks to be fed lengthwise in timed batches.

Synchronizing the in-feed assembly, folding, pulling and clamping assembly and peeling plate is achieved with digitally controlled sensors (dual encoder, proximity sensor), electric solenoids, air cylinders and servo motors. Components can also be mechanically interconnected (e.g. by gears, cams, linkages and pivot arms) to provide the same desired synchronization if one is inclined to do so.

The frame 13 may comprise steel structural elements configured out of square tubing to support the weight of the ribbon decorticating assembly, while taking into account the weight and momentum of both peeling plates moving counter to one another.

The infeed assembly may comprise: guides for the stalks; a set of soft rubber rollers for receiving stalks of different thicknesses that feed into another set of rubber rollers that slightly flatten each plant stalk into two substantially planar stalk sides, adjoined at their edges; and set of feed rollers for frictionally engaging the flattened stalks and forcing the flattened stalks against a splitter’s 2 knife head. Sets of rollers are provided in an opposing configuration and arranged to passively or actively apply force to crush and flatten the stalks. Degumming of the plant stalks epidermis may be performed prior to downstream spinning and can be added to the machine by placing rubber paddle wheels between two sets of in-feed rollers. By spinning the paddles at a higher speed than the infeed rollers, the epidermis of the plant or ‘bark’ is rubbed off prior to its being split into two planar sides, thus eliminating the need for degumming as a separate operation prior to spinning.

The splitter assembly 2 may comprise: a generally V-shaped splitter with a sharp knife-head made of tempered steel. Two sections of stationary chutes 3 follow the knife-head’s contour to provide smooth passage of each planar stalk half. Post-splitter assembly, the machine may comprise two mirror paths and assemblies for bending and peeling respective stalk halves. The following describes the assemblies and operation on a single stalk half.

The folding assembly 4 may comprise: a bending chute for receiving stalk halves, which may be 3D-printed PETG; an eccentric linkage that rotates the bending chute to an orientation away from and substantially parallel to the stalk stationary chute 3; a clamp 5 mounted at the end of each bending chute that holds the stalk half in place during the chute’s movement. The clamp may be actuated by an electrical solenoid or pneumatic cylinder just before and during bending. The clamp actuates to grip the stalk half when the mid-point of the stalk half is approximately at the junction of the stationary chute 3 and bending chute 21 (aka aft and fore chutes respectively). Sensors determine when the stalk pieces ends are located proximate the clamp and then activates the clamp. The rate of linear movement provided by the in-feed rollers is matched by the motion of the bending chute. The in-feed assembly continues to force the whole stalk across the splitter causing the stalk’s hurd 16 to continue the trajectory from the stalk stationary chute 3, while its outer bast begins to peel away at its breakpoint (greater than 45 °). The length to the breakpoint depends on the travel of the hinged chute. The length of bast spanning the gap between the broken segments grows until the bending chute 21 bends and travels away from the stationary chute 3, at which point the clamps 5 opens to release the planar stalk halves, in preparation for the peeling plate 11 to contact the bast.

The peeling plates assembly comprises: hub 19; curved peeling plates located on opposed sides of the hub; a shaft rotatably mounted to the hub and connected to the peeling plate 11 for rotational movement; and a pair of passive roller/wiper 9 biased to maintain contact with the peeling plates as it rotates therepast. The peeling plates have an arc length sized to the broken stalk length (i.e. half of the length of stalk 8). The plates are curved in a constant radius about the hub. Each peeling plate has a peeling plate head that is rounded on the leading edge, preferably similar to the leading edge of an aircraft wing. The edges of the stationary and bending chutes are also preferably rounded to prevent tearing of the bast under tension. These rounded edges abut each other in the initial aligned orientation and may be curved / arcuate in profile or comprise rollers. As shown in FIG. 11 , the tensioning roller is positioned and configured to abut the peeling plate to match the in-feed rollers propelling the planar stalk upwards by maintaining a force between the bast and peeling plate until the bast ribbon is completely separated from the remaining planar stalk. The rounded edge 19 acts on the bast to encourage bast-hurd separation without cutting through it.

After the peeling plate performs its peeling function, remnants of the bast remain on the plate. The base may be removed by a wiper contacting the leading edge of the peeling plate. The wiper may be a conveyor assembly 20 comprises: a high-speed rotating reinforced rubber belt (or similar) belt located to contact each peeling plate’s leading edge as it rotates past, with the belt oriented at an angle to the leading edge, so as to progressively contact portions of the peeling plate, rather than simultaneously contacting the full length of the peeling plate, as the belt would if it were parallel to the leading edge. The conveyor may contact the leading third of the peeling plate, as it sweeps through. The belt preferably includes asymmetrical V notches configured to dislodge bast remnant folded about the leading edge of the peeling head.

As shown in the FIG. 12 , the two portions of hurd 17 leaves the machine via discharge chutes 10 that are preferably air assisted and orientated for receiving hurd from the vicinity of the break, that is the aft end of folding chute and end of stationary chute 3. The chutes shown in the drawings are simple troughs relying on gravity to move the hurd as desired. The hurd discharge chutes could include a means for positively moving the hurd, for example conveyor belts, shaker tables, or directly into a chipper.

For dual-purpose hemp varieties, it would be preferred to modify an agricultural swather to cut off anything over 1 to 2 meters, depending on the height of the seed laden canopy and convey it off to the side and lay it gently onto the field. The lower portion is pushed over a lower sickle bar, raised 10-15 cms off the ground (once bast becomes consistent in color) using a modified paddle header and onto a bucket elevator, timed to the onboard ribbon decorticator cycle. Attached to the rear of the vehicle would be modified round balers that collect the peeled bast. Accompanying the vehicle, a trailer would receive chipped hurd from a discharge blower.

For fiber-only varieties, the canopy where branching begins is first cut off using a modified swather and conveyed off to the ground. The remaining stalk is then cut midway, then again at 10-15 cms off the ground and laid into two parallel rows that would be allowed to dry out on the field. Valtech group has

recently commercialized such a piece of equipment. For stationary decortication, the lower two portions of stalk would be handled in a similar manner to textile flax, using modified flax balers to collect the stalks off the field once dry. Unwinding of the rolls would be performed semi-manually, loaded similar to how a chair lift loads before carrying the rows of standing stalks to an escalator where they are lifted into the infeed rollers in time with the peeling plate cycle.

It will be apparent that the decorticating device is configured to simultaneously receive and process numerous plant stalks in a single row and do so continuously. However, for simplicity, in what follows, the operation of the decorticating device is described with respect to a single plant stalk at the point of separation.

In use, stalks from the field are fed into the infeed rollers. The rollers are continuously rolling and pull the stalk in while crushing it into two planar halves, which are connected to each other at the edges by fibers. The splitter automatically splits the halves into two stalk halves as the feed rollers continue to push the stalk. The stalk halves enter the stationary chute then enter the bending chute 21. As the stalk halves has passed halfway into the chute 4, a proximity sensor actuates the clamp 5 at the end of the bending chute. Simultaneously an eccentric linkage 6 rotates the bending chute away from the stationary chute 3. Once the bending chute reaches ~45 degrees relative to the stationary chute 3, a linear motor 7 moves the bending chute away from the stationary chute 3 at the speed of the infeed rollers (adjustable from 10-22 cms/sec). At a point greater than 45°, the planar stalk breaks its hurd core, but the bending chute 21 continues to bend and move away. This causes the planar stalk still being fed by the in-feed rollers to force the hurd upwards while the clamped bast is forced towards the edge of the moving bending chute. The ends of bending chute 21 and stationary chute 3 are rounded to reduce friction on the bast as its peeled. Bast connected to the folding chute side stays adhered to the planar stalk while the stationary chute side peels against the acute angle formed by the folding chute. After both movements are complete the clamp 5 opens again to release the planar stalk halves.

Rotation of the peeling plates bring the leading edge of one of the blunt faced plates into contact with the inside surface of the bast extending between the edge of the stationary chute and the edge of the folded chute Further movement of the peeling plate causes the bast to fold about the leading edge at an even more acute angle to both chutes, which draws the bast away from its hurd at the relative speed of the peeling plate towards air assisted chutes that eject the hurd, now freed of its outer bast. The inner hurd follows the direction of the chutes and is propelled the opposite direction of the peeling head with such force as to launch them in the air before being caught by hurd discharge slides. The passive tensioning roller 9 makes contact for the entire length of the peeling plate to keep the bast adhered to the peeling plate while the planar stalk is being pushed past the splitting head by the infeed rollers.

Once the peeling plate clears the bender assembly and tensioning roller, the eccentric linkage causes the bending chute to rotate backwards, while the linear motor moves the chute back to its original position aligned with the stationary chute.

Further rotation of the peeling plate shaft brings the leading edge of the peeling plate (about which the bast is folded on) into contact with the high-speed rotating belt, which dislodges the bast from the peeling head and conveys the bast laterally away from the frame. It is preferable to have the bast ribbons be brought into a modified round baler to be wound into bales of ribbon for manageable downstream processing of said ribbon (drying, carding, whitening, spinning). 

1. A method for decorticating a length of a plant stalk, the method comprising: a) passing the length of plant stalk between opposed rollers to flatten the plant stalk into two substantially planar stalk sides with adjoining edges; b) interposing and passing a splitter between the two stalk sides so as to sever the adjoined edges, creating two stalk pieces, each comprising a bast layer and hurd; c) supporting fore and aft sections of each stalk piece in fore and aft chutes, d) rotating the fore and aft chutes with respect to each other to bend each stalk piece, with the hurd on an outer radius and bast on an inner radius until the hurd is broken, without severing the bast layer; e) peeling the bast layer from the hurd by acting on a section of the bast layer connecting the broken hurd pieces and moving that section of the bast layer away from the broken, supported stalk pieces; and f) ejecting the bast layer and hurd to collection locations.
 2. The method of claim 1, wherein the peeled bast forms an acute angle with the unpeeled bast at a point of peeling off the hurd.
 3. The method of claim 1, wherein peeling occurs at substantially rounded edges of the fore and aft chutes.
 4. The method of claim 1, wherein the step of peeling is provided by a peeling plate abutting an inner surface of the bast.
 5. The method of claim 4, further comprising wiping the bast from the peeling plate.
 6. The method of claim 1, further comprising, during peeling, moving the broken stalk pieces in a direction generally opposite the movement of the section of bast connecting said broken stalk pieces.
 7. The method of claim 1, further comprising gripping the stalk pieces in the chutes during bending.
 8. The method of claim 1, wherein, during bending, the fore and aft chutes contain substantially equal portions of the stalk pieces and the chutes rotate relative to each other to break the hurd at substantially mid-length.
 9. The method of claim 8, wherein the fore and aft chutes rotate relative to each other, from an aligned orientation to substantially parallel orientation.
 10. The method of claim 1, further comprising urging the peeled bast into contact with the peeling plate during peeling, preferably using a passive roller.
 11. The method of claim 1, further comprising moving the fore chute away from the aft chute, after breaking the hurd that continues to be driven through the splitter and rollers.
 12. Apparatus for decorticating a length of a plant stalk comprising: opposed rollers for receiving and flattening the plant stalk into two substantially planar stalk sides with adjoining edges; a splitter positioned downstream of the rollers, so as to sever the adjoined edges, creating two stalk pieces, each comprising a bast layer and hurd; fore and aft chutes for receiving and supporting the stalk pieces; an actuator for rotating the fore and aft chutes relative to each other to bend and break the stalk pieces, without severing the bast layer; a peeling plate moveable between fore and aft chutes for peeling the bast layer from the hurd; and ejection chutes for ejecting the bast layer and hurd to collection locations.
 13. The apparatus of claim 12, wherein the fore and aft chutes rotate relative to each other, from an aligned orientation to a substantially parallel orientation.
 14. The apparatus of claim 12, wherein the fore and aft chutes comprise rounded edges.
 15. The apparatus of claim 12, further comprising a wiper engaging a leading edge of the peeling plate.
 16. The apparatus of claim 12, further comprising clamps in the fore chutes for holding stalk pieces during bending.
 17. The apparatus of claim 12, further comprising a roller biased against the peeling plate during peeling. 